Levi is right. there’s nothing arbitrary about it. i own a bar in Brooklyn and have my name on a liquor license. NYS SLA law specifically says (or at least last time i checked a few years ago) anyone up to 16 yo must be accompanied by a parent or guardian, and no one btwn the ages of 17-20 is allowed to enter the establishment under any circumstances. it makes perfect sense. if you think about it, if some of-age folks come in with their 17-18 yo kids, it would be very easy for me or my bartenders to accidentally serve them, thinking they must be old enough to drink. they can look old enough, act old enough, and be so nonchalant about it that we wouldn’t even question it. now, a 14yo on the other hand....
whether an establishment chooses to obey this law is another thing altogether, but since my livelihood is of most importance to me, i certainly do.